E20
SPRSUN
Communication Error with External Controller / BMS
Display shows E20; unit may not respond to remote or Wi-Fi app.
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Safety Warning
This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.
If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.
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Possible Causes
Incorrect RS485 or Modbus wiring, Loose communication terminals, Wrong protocol settings, Faulty communication module
How to Fix / Troubleshooting
Safety first: Turn off power before adjusting communication wiring.
- Check wiring polarity: Verify that A/B (or +/−) terminals on the SPRSUN heater match the external controller or BMS wiring.
- Tighten terminals: Ensure all RS485 or communication terminals are tight and free of corrosion.
- Verify settings: Confirm baud rate, address, and protocol settings on both the heater and external controller match the SPRSUN documentation.
- Isolate the bus: Temporarily disconnect other devices on the bus to see if E20 clears when only the heater is connected.
- Replace module: If wiring and settings are correct, the communication module or main PCB may need replacement.
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Repair Difficulty
Hard
4/5
Required Part
RS485 Communication Module
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